Performance & Maintenance

Panels are typically warranted for 25 to 30 years on performance, and they do not stop working at the end of that. What is warranted is output: most manufacturers guarantee around 85 to 90 per cent of the original figure at year 25. The inverter is the component with a shorter life, usually 10 to 15 years, and it is the part most likely to need replacing during the system's lifetime. Budget for that rather than being surprised by it.

Panels degrade slowly and predictably, typically a little under half a per cent a year after the first year. In practice that means a system producing 4,000 kWh today produces roughly 3,600 kWh after twenty years. It is a gradual decline rather than a cliff, and it is already accounted for in any honest payback estimate.

In Irish weather, generally no. Rain does most of the work, and panels are mounted at an angle that helps. Cleaning is worth considering if you are under trees, near agricultural dust, or somewhere gulls are a problem. If you do, it is a job for someone on the roof safely, not a brush from a ladder.

Yes, if the system is set up to tell you. Most modern inverters report generation to an app, so a drop in output is visible. Without monitoring, a failed panel or a tripped inverter can go unnoticed for months, which is the single most common reason a system quietly underperforms. Ask for monitoring to be included and shown to you at handover.

More than people expect. Panels in a string can be affected by shade falling on one of them, so a single chimney, dormer or branch can cost more than its size suggests. This is why the survey looks at obstructions before it looks at roof area, and why optimisers or a different string layout are sometimes worth the extra.